Lens element

ABSTRACT

A lens element worn in front of an eye of a person includes a refraction area having a first refractive power based on a prescription for correcting an abnormal refraction of the eye of the person and a second refractive power different from the first refractive power and a plurality of at least three optical elements, at least one optical element having an optical function of not focusing an image on the retina of the eye so as to slow down the progression of the abnormal refraction of the eye.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 16/976,662, filed Aug. 28, 2020, which is a National StageApplication of International Application No. PCT/EP2019/055216, filedMar. 1, 2019, which is based upon and claims the benefit of priorityfrom European Patent Application No. 18305527.6, filed on Apr. 26, 2018,European Patent Application No. 18305526.8, filed on Apr. 26, 2018,European Patent Application No. 18305436.0, filed on Apr. 11, 2018,European Patent Application No. 18305435.2, filed on Apr. 11, 2018,European Patent Application No. 18305385.9, filed on Mar. 30, 2018,European Patent Application No. 18305384.2, filed on Mar. 30, 2018,European Patent Application No. 18305217.4, filed on Mar. 1, 2018, andEuropean Patent Application No. 18305216.6, filed on Mar. 1, 2018, theentire contents of which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a lens element intended to be worn in front ofan eye of a person to suppress progression of abnormal refractions ofthe eye such as myopia or hyperopia.

BACKGROUND OF THE INVENTION

Myopia of an eye is characterized by the fact that the eye focusesdistant objects in front of its retina. Myopia is usually correctedusing a concave lens and hyperopia is usually corrected using a convexlens.

It has been observed that some individuals when corrected usingconventional single vision optical lenses, in particular children, focusinaccurately when they observe an object which is situated at a shortdistance away, that is to say, in near vision conditions. Because ofthis focusing defect on the part of a myopic child which is correctedfor his far vision, the image of an object close by is also formedbehind his retina, even in the foveal area.

Such focusing defect may have an impact on the progression of myopia ofsuch individuals. One may observe that for most of said individual themyopia defect tends to increase over time.

Therefore, it appears that there is a need for a lens element that wouldsuppress or at least slow down progression of abnormal refractions ofthe eye such as myopia or hyperopia.

SUMMARY OF THE INVENTION

To this end, the invention proposes a lens element intended to be wornin front of an eye of a person comprising:

-   -   a refraction area having a first refractive power based on a        prescription for correcting an abnormal refraction of said eye        of the person and a second refractive power different from the        first refractive power;    -   a plurality of at least three optical elements, at least one        optical element having an optical function of not focusing an        image on the retina of the eye so as to slow down the        progression of the abnormal refraction of the eye.

Advantageously, having a second refractive power different from thefirst refractive power for correcting the abnormal refraction of the eyeof the person in the refraction area allows increasing the defocus ofthe light rays in front the retina in case of myopia.

In other words, the inventors have observed that having in therefraction area a second refractive power different from the refractivepower for correcting the abnormal refraction combined with opticalelements having an optical function of not focusing an image on theretina of the eye helps slow down the progression of abnormal refractionof the eye such as myopia or hyperopia.

The solution of the invention also helps improve the aesthetics of thelens and helps compensate accommodative lag.

According to further embodiments which can be considered alone or incombination:

-   -   the difference between the first refractive power and the second        refractive power is greater than or equal to 0.5 D; and/or    -   the refractive area is formed as the area other than the areas        formed as the plurality of optical elements; and/or    -   at least one optical element has a non-spherical optical        function; and/or    -   at least one, for example all, of the optical elements has an        optical function of focusing an image on a position other than        the retina; and/or    -   in the refractive area the refractive power has a continuous        variation; and/or    -   in the refractive area the refractive power has at least one        discontinuity; and/or    -   the lens element is divided in five complementary zones, a        central zone having a power being equal to the first refractive        power and four quadrants at 45°, at least one of the quadrant        having a refractive power equal to the second refractive power;        and/or    -   the central zone comprises a framing reference point that faces        the pupil of the person gazing straight ahead in standard        wearing conditions and has a diameter greater than 4 mm and        smaller than 20 mm; and/or    -   at least lower part quadrant has the second refractive power;        and/or    -   the refraction area has a progressive addition dioptric        function; and/or    -   at least one of the temporal and nasal quadrant has the second        refractive power; and/or    -   the four quadrants have a concentric power progression; and/or    -   for every circular zone having a radius comprised between 2 and        4 mm comprising a geometrical center located at a distance of        the framing reference that faces the pupil of the user gazing        straight ahead in standard wearing conditions greater or equal        to said radius +5 mm, the ratio between the sum of areas of the        parts of optical elements located inside said circular zone and        the area of said circular zone is comprised between 20% and 70%;        and/or    -   the at least three optical elements are non-contiguous; and/or    -   at least one of the optical elements is a spherical micro-lens;        and/or    -   at least one of the optical elements is a multifocal refractive        micro-lens; and/or    -   the at least one multifocal refractive micro-lens comprises an        aspherical surface, with or without any rotational symmetry;        and/or    -   at least one of the optical elements is a toric refractive        micro-lens; and/or    -   at least one of the optical elements is a cylindrical        micro-lens; and/or    -   the at least one multifocal refractive micro-lens comprises a        toric surface; and/or    -   at least one of the optical elements is made of a birefringent        material; and/or    -   at least one of the optical elements is a diffractive lens;        and/or    -   the at least one diffractive lens comprises a metasurface        structure; and/or    -   at least one optical elements has a shape configured so as to        create a caustic in front of the retina of the eye of the        person; and/or    -   at least one optical element is a multifocal binary component;        and/or    -   at least one optical element is a pixelated lens; and/or    -   at least one optical element is a π-Fresnel lens; and/or    -   at least part, for example all, of the optical elements are        located on the front surface of the ophthalmic lens; and/or    -   at least part, for example all, of the optical elements are        located on the back surface of the ophthalmic lens; and/or    -   at least part, for example all, of the optical elements are        located between the front and the back surfaces of the        ophthalmic lens; and/or    -   at least part, for example all, optical functions comprise high        order optical aberrations; and/or    -   the lens element comprises an ophthalmic lens bearing the        refraction area and a clip-on bearing the plurality of at least        three optical elements adapted to be removably attached to the        ophthalmic lens when the lens element is worn; and/or    -   the optical elements are configured so that along at least one        section of the lens the mean sphere of optical elements        increases from a point of said section towards the peripheral        part of said section; and/or    -   the optical elements are configured so that along at least one        section of the lens the mean cylinder of optical elements        increases from a point of said section towards the peripheral        part of said section; and/or    -   the optical elements are configured so that along the at least        one section of the lens the mean sphere and/or the mean cylinder        of optical elements increases from the center of said section        towards the peripheral part of said section; and/or    -   the refraction area comprises an optical center and optical        elements are configured so that along any section passing        through the optical center of the lens the mean sphere and/or        the mean cylinder of the optical elements increases from the        optical center towards the peripheral part of the lens; and/or    -   the refraction area comprises a far vision reference point, a        near vision reference, and a meridian joining the far and near        vision reference points, the optical elements are configured so        that in standard wearing conditions along any horizontal section        of the lens the mean sphere and/or the mean cylinder of the        optical elements increases from the intersection of said        horizontal section with the meridian towards the peripheral part        of the lens; and/or    -   the mean sphere and/or the mean cylinder increase function along        the sections are different depending on the position of said        section along the meridian; and/or    -   the mean sphere and/or the mean cylinder increase function along        the sections are unsymmetrical; and/or    -   the optical elements are configured so that in standard wearing        condition the at least one section is a horizontal section;        and/or    -   the mean sphere and/or the mean cylinder of optical elements        increases from a first point of said section towards the        peripheral part of said section and decreases from a second        point of said section towards the peripheral part of said        section, the second point being closer to the peripheral part of        said section than the first point; and/or    -   the mean sphere and/or the mean cylinder increase function along        the at least one horizontal section is a Gaussian function;        and/or    -   the mean sphere and/or the mean cylinder increase function along        the at least one horizontal section is a Quadratic function;        and/or    -   at least one, for example at least 70%, for example all optical        elements are active optical element that may be activated by an        optical lens controller device; and/or    -   the active optical element comprises a material having a        variable refractive index whose value is controlled by the        optical lens controller device; and/or    -   at least one optical element has a contour shape inscribable in        a circle having a diameter greater than or equal to 0.8 mm and        smaller than or equal to 3.0 mm; and/or    -   the optical elements are positioned on a network; and/or    -   the network is a structured network; and/or    -   the structured network is a squared network or a hexagonal        network or a triangle network or an octagonal network; and/or    -   the lens element further comprises at least four optical        elements organized in at least two groups of optical elements;        and/or    -   each group of optical element is organized in at least two        concentric rings having the same center, the concentric ring of        each group of optical element being defined by an inner diameter        corresponding to the smallest circle that is tangent to at least        one optical element of said group and an outer diameter        corresponding to the largest circle that is tangent to at least        one optical elements of said group; and/or    -   at least part of, for example all the concentric rings of        optical elements are centered on the optical center of the        surface of the lens element on which said optical elements are        disposed; and/or    -   the concentric rings of optical elements have a diameter        comprised between 9.0 mm and 60 mm; and/or    -   the distance between two successive concentric rings of optical        elements is greater than or equal to 5.0 mm, the distance        between two successive concentric rings being defined by the        difference between the inner diameter of a first concentric ring        and the outer diameter of a second concentric ring, the second        concentric ring being closer to the periphery of the lens        element.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the invention will now be described withreference to the accompanying drawing wherein:

FIG. 1 is a plan view of a lens element according to the invention;

FIG. 2 is a general profile view of a lens element according to theinvention;

FIG. 3 represents an example of a Fresnel height profile;

FIG. 4 represents an example of a diffractive lens radial profile;

FIG. 5 illustrates a π-Fresnel lens profile;

FIGS. 6a to 6c illustrate a binary lens embodiment of the invention;

FIG. 7a illustrates the astigmatism axis γ of a lens in the TABOconvention;

FIG. 7b illustrates the cylinder axis γ_(AX) in a convention used tocharacterize an aspherical surface; and

FIG. 8 is a plan view of a lens element according to an embodiment ofthe invention.

Elements in the figures are illustrated for simplicity and clarity andhave not necessarily been drawn to scale. For example, the dimensions ofsome of the elements in the figure may be exaggerated relative to otherelements to help to improve the understanding of the embodiments of thepresent invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention relates to a lens element intended to be worn in front ofan eye of a person.

In the reminder of the description, terms like «up », «bottom »,«horizontal », «vertical », «above », «below », «front », «rear » orother words indicating relative position may be used. These terms are tobe understood in the wearing conditions of the lens element.

In the context of the present invention, the term “lens element” canrefer to an uncut optical lens or a spectacle optical lens edged to fita specific spectacle frame or an ophthalmic lens and an optical deviceadapted to be positioned on the ophthalmic lens. The optical device maybe positioned on the front or back surface of the ophthalmic lens. Theoptical device may be an optical patch. The optical device may beadapted to be removably positioned on the ophthalmic lens for example aclip configured to be clipped on a spectacle frame comprising theophthalmic lens.

A lens element 10 according to the invention is adapted for a person andintended to be worn in front of an eye of said person.

As represented on FIG. 1, a lens element 10 according to the inventioncomprises:

-   -   a refraction area 12, and    -   a plurality of at least three optical elements 14.

The refraction area 12 has a first refractive power P1 based on theprescription of the eye of the person for which the lens element isadapted. The prescription is adapted for correcting the abnormalrefraction of the eye of the person.

The term “prescription” is to be understood to mean a set of opticalcharacteristics of optical power, of astigmatism, of prismaticdeviation, determined by an ophthalmologist or optometrist in order tocorrect the vision defects of the eye, for example by means of a lenspositioned in front of his eye. For example, the prescription for amyopic eye comprises the values of optical power and of astigmatism withan axis for the distance vision.

The refractive area 12 further comprises at least a second refractivepower P2 different from the first refractive power P1.

In the sense of the invention, the two refractive powers are considereddifferent when the difference between the two refractive powers isgreater than or equal to 0.5 D.

When the abnormal refraction of the eye of the person corresponds tomyopia the second refractive power is greater than the first refractivepower.

When the abnormal refraction of the eye of the person corresponds tohyperopia, the second refractive power is smaller than the firstrefractive power.

The refractive area is preferably formed as the area other than theareas formed as the plurality of optical elements. In other words, therefractive area is the complementary area to the areas formed by theplurality of optical elements.

The refractive area may have a continuous variation of refractive power.For example, the refractive area may have a progressive addition design.

The optical design of the refraction area may comprise

-   -   a fitting cross where the optical power is negative,    -   a first zone extending in the temporal side of the refractive        are when the lens element is being worn by a wearer. In the        first zone, the optical power increases when moving towards the        temporal side, and over the nasal side of the lens, the optical        power of the ophthalmic lens is substantially the same as at the        fitting cross.

Such optical design is disclosed in greater details in W02016/107919.

Alternatively, the refractive power in the refractive area may compriseat least one discontinuity.

As represented on FIG. 1, the lens element may be divided in fivecomplementary zones, a central zone 16 having a power being equal to thefirst refractive power and four quadrants Q1, Q2, Q3, Q4 at 45°, atleast one of the quadrant having at least a point where the refractivepower is equal to the second refractive power.

In the sense of the invention the “quadrants at 45°” are to beunderstood as equal angular quadrant of 90° oriented in the directions45°/225° and 135°/315° according to the TABO convention as illustratedon FIG. 1.

Preferably, the central zone 16 comprises a framing reference point thatfaces the pupil of the person gazing straight ahead in standard wearingconditions and has a diameter greater than or equal to 4 mm and smallerthan or equal to 22 mm.

The wearing conditions are to be understood as the position of the lenselement with relation to the eye of a wearer, for example defined by apantoscopic angle, a Cornea to lens distance, a Pupil-cornea distance, acentre of rotation of the eye (CRE) to pupil distance, a CRE to lensdistance and a wrap angle.

The Cornea to lens distance is the distance along the visual axis of theeye in the primary position (usually taken to be the horizontal) betweenthe cornea and the back surface of the lens; for example equal to 12 mm.

The Pupil-cornea distance is the distance along the visual axis of theeye between its pupil and cornea; usually equal to 2 mm.

The CRE to pupil distance is the distance along the visual axis of theeye between its center of rotation (CRE) and cornea; for example equalto 11.5 mm.

The CRE to lens distance is the distance along the visual axis of theeye in the primary position (usually taken to be the horizontal) betweenthe CRE of the eye and the back surface of the lens, for example equalto 25.5 mm.

The pantoscopic angle is the angle in the vertical plane, at theintersection between the back surface of the lens and the visual axis ofthe eye in the primary position (usually taken to be the horizontal),between the normal to the back surface of the lens and the visual axisof the eye in the primary position; for example equal to −8°.

The wrap angle is the angle in the horizontal plane, at the intersectionbetween the back surface of the lens and the visual axis of the eye inthe primary position (usually taken to be the horizontal), between thenormal to the back surface of the lens and the visual axis of the eye inthe primary position for example equal to 0°.

An example of standard wearer condition may be defined by a pantoscopicangle of −8°, a Cornea to lens distance of 12 mm, a Pupil-corneadistance of 2 mm, a CRE to pupil distance of 11.5 mm, a CRE to lensdistance of 25.5 mm and a wrap angle of 0°.

According to an embodiment of the invention at least the lower partquadrant Q4 has a second refractive power different from the firstrefractive power corresponding to the prescription for correcting theabnormal refraction.

For example, the refractive area has a progressive addition dioptricfunction. The progressive addition dioptric function may extend betweenthe upper part quadrant Q2 and the lower part quadrant Q4.

Advantageously, such configuration allows compensation of accommodativelag when the person looks for example at near vision distances thanks tothe addition of the lens.

According to an embodiment, at least one of the temporal Q3 and nasal Q1quadrant has the second refractive power. For example, the temporal Q3quadrant has a variation of power with the eccentricity of the lens.

Advantageously, such configuration increases the efficiency of theabnormal refraction control in peripheral vision with even more effectin horizontal axis.

According to an embodiment, the four quadrants Q1, Q2, Q3 and Q4 have aconcentric power progression.

At least one optical element of the plurality of at least three opticalelements 14, has an optical function of not focusing an image on theretina of the eye of the person when the lens element is worn instandard wearing conditions.

Advantageously, such optical function of the optical element combinedwith a refractive area having at least one refractive power differentfrom the refractive power of the prescription allows slowing down theprogression of the abnormal refraction of the eye of the person wearingthe lens element.

The optical elements may be as represented on FIG. 1, non-contiguousoptical elements.

In the sense of the invention two optical elements are non-contiguous iffor all the paths linking the two optical elements one may measure atleast along part of each path the refractive power based on aprescription for the eye of the person.

When the two optical elements are on a spherical surface, the twooptical elements are non-contiguous if there for all the paths linkingthe two optical elements one may measure at least along part of eachpath the curvature of said spherical surface. As illustrated on FIG. 2,a lens element 10 according to the invention comprises an object sidesurface F1 formed as a convex curved surface toward an object side, andan eye side surface F2 formed as a concave surface having a differentcurvature than the curvature of the object side surface F1.

According to an embodiment of the invention, at least part, for exampleall, of the optical elements are located on the front surface of thelens element.

At least part, for example all, of the optical elements may be locatedon the back surface of the lens element.

At least part, for example all, of the optical elements may be locatedbetween the front and back surfaces of the lens element. For example,the lens element may comprise zones of different refractive indexforming the optical elements.

According to an embodiment of the invention, the central zone of thelens corresponding to a zone centered on the optical center of the lenselement does not comprise optical elements. For example, the lenselement may comprise an empty zone centered on the optical center ofsaid lens element and having a diameter equal to 0.9 mm which does notcomprise optical elements.

The optical center of the lens element may correspond to the fittingpoint of the lens.

Alternatively, the optical elements may be disposed on the entiresurface of the lens element.

According to embodiments of the invention, the optical elements arepositioned on a network.

The network on which the optical elements are positioned may be astructured network.

In the embodiments illustrated on FIG. 8 the optical elements arepositioned along a plurality of concentric rings.

The concentric rings of optical elements may be annular rings.

According to an embodiment of the invention, the lens element furthercomprises at least four optical elements. The at least four opticalelements are organized in at least two groups of optical elements, eachgroup of optical element being organized in at least two concentricrings having the same center, the concentric ring of each group ofoptical element being defined by an inner diameter and an outerdiameter.

The inner diameter of a concentric ring of each group of opticalelements corresponds to the smallest circle that is tangent to at leastone optical element of said group of optical elements. The outerdiameter of a concentric ring of optical element corresponds to thelargest circle that is tangent to at least one optical element of saidgroup.

For example, the lens element may comprise n rings of optical elements,f_(inner 1) referring to the inner diameter of the concentric ring whichis the closest to the optical center of the lens element, f _(outer 1)referring to the outer diameter of the concentric ring which is theclosest to the optical center of the lens element, f _(inner n)referring to the inner diameter of the ring which is the closest to theperiphery of the lens element, and f _(outer n) referring to the outerdiameter of the concentric ring which is the closest to the periphery ofthe lens element.

The distance D_(i) between two successive concentric rings of opticalelements i and i+1 may be expressed as:D _(i) =|f _(inner i+1) −f _(outer i)|,

wherein f_(outer i) refers to the outer diameter of a first ring ofoptical elements i and f_(inner i+1) refers to the inner diameter of asecond ring of optical elements i+1 that is successive to the first oneand closer to the periphery of the lens element.

According to another embodiment of the invention, the optical elementsare organized in concentric rings centered on the optical center of thesurface of the lens element on which the optical elements are disposedand linking the geometrical center of each optical element.

For example, the lens element may comprise n rings of optical elements,f₁ referring to the diameter of the ring which is the closest to theoptical center of the lens element and f_(n) referring to the diameterof the ring which is the closest to the periphery of the lens element.

The distance D_(i) between two successive concentric rings of opticalelements i and i+1 may be expressed as:

${D_{i} = {{f_{i + 1} - f_{i} - \frac{d_{i + 1}}{2} - \frac{d_{i}}{2}}}},$

wherein f_(i), refers to the diameter of a first ring of opticalelements i and f_(i+1) refers to the diameter of a second ring ofoptical elements i+1 that is successive to the first one and closer tothe periphery of the lens element, and

wherein d_(i), refers to the diameter of the optical elements on thefirst ring of optical elements and d_(i+1) refers to the diameter of theoptical elements on the second ring of optical elements that issuccessive to the first ring and closer to the periphery of the lenselement. The diameter of the optical element corresponds to the diameterof the circle in which the contour shape of the optical element isinscribed.

The concentric rings of optical elements may be annular rings.

Advantageously, the optical center of the lens element and the center ofthe concentric rings of optical elements coincide. For example, thegeometrical center of the lens element, the optical center of the lenselement, and the center of the concentric rings of optical elementscoincide.

In the sense of the invention, the term coincide should be understood asbeing really close together, for example distanced by less than 1.0 mm.

The distance D_(i) between two successive concentric rings may varyaccording to i. For example, the distance D_(i) between two successiveconcentric rings may vary between 2.0 mm and 5.0 mm.

According to an embodiment of the invention, the distance D_(i) betweentwo successive concentric rings of optical elements is greater than 2.00mm, preferably 3.0 mm, more preferably 5.0 mm.

Advantageously, having the distance D_(i) between two successiveconcentric rings of optical elements greater than 2.00 mm allowsmanaging a larger refraction area between these rings of opticalelements and thus provides better visual acuity.

Considering an annular zone of the lens element having an inner diametergreater than 9 mm and an outer diameter smaller than 57 mm, having ageometrical center located at a distance of the optical center of thelens element smaller than 1 mm, the ratio between the sum of areas ofthe parts of optical elements located inside said circular zone and thearea of said circular zone is comprised between 20% and 70%, preferablybetween 30% and 60%, and more preferably between 40% and 50%.

In other words, the inventors have observed that for a given value ofthe abovementioned ratio, the organization of optical elements inconcentric rings, where these rings are spaced by a distance greaterthan 2.0 mm, allows providing annular zones of refractive area easier tomanufacture than the refractive area managed when optical element aredisposed in hexagonal network or randomly disposed on the surface of thelens element. thereby provide a better correction of the abnormalrefraction of the eye and thus a better visual acuity.

According to an embodiment of the invention, the diameter di of alloptical elements of the lens element are identical.

According to an embodiment of the invention, the distance D_(i) betweentwo successive concentric rings i and i+1 may increase when i increasestowards the periphery of the lens element.

The concentric rings of optical elements may have a diameter comprisedbetween 9 mm and 60 mm.

According to an embodiment of the invention, the lens element comprisesoptical elements disposed in at least 2 concentric rings, preferablymore than 5, more preferably more than 10 concentric rings. For example,the optical elements may be disposed in 11 concentric rings centered onthe optical center of the lens.

According to an embodiment of the invention, at least one of the opticalelements has an optical function of focusing an image on a positionother than the retina.

Preferably, at least 50%, for example at least 80%, for example all, ofthe optical elements have an optical function of focusing an image on aposition other than the retina.

According to an embodiment of the invention, the optical elements areconfigured so that at least along one section of the lens the meansphere of the optical elements increases from a point of said sectiontowards the periphery of said section.

The optical elements may further be configured so that at least alongone section of the lens, for example at least the same section as theone along which the mean sphere of the optical elements increases, themean cylinder increases from a point of said section, for example thesame point as for the mean sphere, towards the peripheral part of saidsection.

Advantageously, having optical elements configured so that along atleast one section of the lens the mean sphere and/or mean cylinder ofoptical elements increases from a point of said section towards theperipheral part of said section allows increasing the defocus of thelight rays in front the retina in case of myopia or behind the retina incase of hyperopia.

In other words, the inventors have observed that having optical elementsconfigured so that along at least one section of the lens the meansphere of optical elements increases from a point of said sectiontowards the peripheral part of said section helps slow down theprogression of abnormal refraction of the eye such as myopia orhyperopia.

As is known, a minimum curvature CURV_(min) is defined at any point onan aspherical surface by the formula:

${CURV}_{\min} = \frac{1}{R_{\max}}$where R_(max) is the local maximum radius of curvature, expressed inmeters and CURV_(min) is expressed in dioptres.

Similarly, a maximum curvature CURV_(max) can be defined at any point onan aspheric surface by the formula:

${CURV}_{\max} = \frac{1}{R_{\min}}$where R_(min) is the local minimum radius of curvature, expressed inmeters and CURV_(max) is expressed in dioptres.

It can be noticed that when the surface is locally spherical, the localminimum radius of curvature R_(min) and the local maximum radius ofcurvature R_(max) are the same and, accordingly, the minimum and maximumcurvatures CURV_(min) and CURV_(max) are also identical. When thesurface is aspherical, the local minimum radius of curvature R_(min) andthe local maximum radius of curvature R_(max) are different.

From these expressions of the minimum and maximum curvatures CURV_(min)and CURV_(max), the minimum and maximum spheres labeled SPH_(min) andSPH_(max) can be deduced according to the kind of surface considered.

When the surface considered is the object side surface (also referred toas the front surface), the expressions are the following:

${{SPH}_{\min} = {{\left( {n - 1} \right)*{CURV}_{\min}} = \frac{n - 1}{R_{\max}}}},{and}$${SPH}_{\min} = {{\left( {n - 1} \right)*{CURV}_{\min}} = \frac{n - 1}{R_{\max}}}$where n is the refractive index of the constituent material of the lens.

If the surface considered is an eyeball side surface (also referred toas the back surface), the expressions are the following:

${SPH}_{\min} = {{\left( {1 - n} \right)*{CURV}_{\min}} = {\frac{1 - n}{R_{\max}}\mspace{14mu}{and}}}$${SPH}_{\max} = {{\left( {1 - n} \right)*{CURV}_{\max}} = \frac{1 - n}{R_{\min}}}$where n is the refractive index of the constituent material of the lens.

As is well known, a mean sphere SPH_(mean) at any point on an asphericalsurface can also be defined by the formula:

${SPH}_{mean} = {\frac{1}{2}\left( {{SPH}_{\min} + {SPH}_{\max}} \right)}$

The expression of the mean sphere therefore depends on the surfaceconsidered:

if the surface is the object side surface,

${SPH}_{mean} = {\frac{n - 1}{2}\left( {\frac{1}{R_{\min}} + \frac{1}{R_{\max}}} \right)}$

if the surface is an eyeball side surface,

${SPH}_{mean} = {\frac{1 - n}{2}\left( {\frac{1}{R_{\min}} + \frac{1}{R_{\max}}} \right)}$

a cylinder CYL is also defined by the formula CYL=|SPH_(max)−SPH_(min)|.

The characteristics of any aspherical face of the lens may be expressedby the local mean spheres and cylinders. A surface can be considered aslocally aspherical when the cylinder is at least 0.25 diopters.

For an aspherical surface, a local cylinder axis γ_(AX) may further bedefined. FIG. 7a illustrates the astigmatism axis γ as defined in theTABO convention and FIG. 7b illustrates the cylinder axis γ_(AX) in aconvention defined to characterize an aspherical surface.

The cylinder axis γ_(AX) is the angle of the orientation of the maximumcurvature CURV_(max) with relation to a reference axis and in the chosensense of rotation. In the above defined convention, the reference axisis horizontal (the angle of this reference axis is 0°) and the sense ofrotation is counterclockwise for each eye, when looking at thewearer(0°≤γ_(AX)≤180°. An axis value for the cylinder axis γ_(AX) of+45°therefore represents an axis oriented obliquely, which when lookingat the wearer, extends from the quadrant located up on the right to thequadrant located down on the left.

The optical elements may be configured so that that along the at leastone section of the lens the mean sphere and/or the mean cylinder ofoptical elements increases from the center of said section towards theperipheral part of said section.

According to an embodiment of the invention, the optical elements areconfigured so that in standard wearing condition the at least onesection is a horizontal section.

The mean sphere and/or the mean cylinder may increase according to anincrease function along the at least one horizontal section, theincrease function being a Gaussian function. The Gaussian function maybe different between the nasal and temporal part of the lens so as totake into account the dissymmetry of the retina of the person.

Alternatively, the mean sphere and/or the mean cylinder may increaseaccording to an increase function along the at least one horizontalsection, the increase function being a Quadratic function. The Quadraticfunction may be different between the nasal and temporal part of thelens so as to take into account the dissymmetry of the retina of theperson.

According to an embodiment of the invention, the mean sphere and/or themean cylinder of optical elements increases from a first point of saidsection towards the peripheral part of said section and decreases from asecond point of said section towards the peripheral part of saidsection, the second point being closer to the peripheral part of saidsection than the first point.

Such embodiment is illustrated in table 1 that provides the mean sphereof optical elements according to their radial distance to the opticalcenter of the lens element.

In the example of table 1, the optical elements are micro lens placed ona spherical front surface having a curvature of 329.5 mm and the lenselement is made of an optical material having a refractive index of1.591, the prescribed optical power of the wearer is of 6 D. The opticalelement is to be worn in standard wearing conditions and the retina ofthe wearer is considered as having a defocus of 0.8 D at an angle of30°.

TABLE 1 Distance to Mean sphere optical center (mm) of optical element(D) 0 1.992 5 2.467 7.5 2.806 10 3.024 15 2.998 20 2.485

As illustrated in table 1, starting close to the optical center of thelens element, the mean sphere of the optical elements increases towardsthe peripheral part of said section and then decreases towards theperipheral part of said section.

According to an embodiment of the invention, the mean cylinder ofoptical elements increases from a first point of said section towardsthe peripheral part of said section and decreases from a second point ofsaid section towards the peripheral part of said section, the secondpoint being closer to the peripheral part of said section than the firstpoint. Such embodiment is illustrated in tables 2 and 3 that providesthe amplitude of the cylinder vector projected on a first direction Ycorresponding to the local radial direction and a second direction Xorthogonal to the first direction.

In the example of table 2, the optical elements are micro-lenses placedon a spherical front surface having a curvature of 167.81 mm and thelens element is made of a material having a refractive index of 1.591,the prescribed optical power of the wearer is of −6 D. The lens elementis to be worn in standard wearing conditions and the retina of thewearer is considered as having a defocus of 0.8 D at an angle of 30°.The elements are determined to provide a peripheral defocus of 2 D.

In the example of table 3, the optical elements are micro-lenses placedon a spherical front surface having a curvature of 167.81 mm and thelens element is made of a material having a refractive index of 1.591,the prescribed optical power of the wearer is of −1 D. The lens elementis to be worn in standard wearing conditions and the retina of thewearer is considered as having a defocus of 0.8 D at an angle of 30°.The optical elements are determined to provide a peripheral defocus of 2D.

TABLE 2 gazing direction Px Py Cylinder (in degree) (in Diopter) (inDiopter) (in Diopter) 0 1.987 1.987 1.987 18.581 2.317 2.431 2.37427.002 2.577 2.729 2.653 34.594 2.769 2.881 2.825 47.246 2.816 2.6592.7375 57.02 2.446 1.948 2.197

TABLE 3 gazing direction Px Py Cylinder (in degree) (in Diopter) (inDiopter) (in Diopter) 0 1.984 1.984 1.984 18.627 2.283 2.163 2.22327.017 2.524 2.237 2.3805 34.526 2.717 2.213 2.465 46.864 2.886 1.9432.4145 56.18 2.848 1.592 2.22

As illustrated in tables 2 and 3, starting close to the optical centerof the lens element, the cylinder of the optical elements increasestowards the peripheral part of said section and then decreases towardsthe peripheral part of said section.

According to an embodiment of the invention, the refraction areacomprises an optical center and optical elements are configured so thatalong any section passing through the optical center of the lens themean sphere and/or the mean cylinder of the optical elements increasesfrom the optical center towards the peripheral part of the lens.

For example, the optical elements may be regularly distributed alongcircles centered on the optical center of the refraction area.

The optical elements on the circle of diameter 10 mm and centered on theoptical center of the refraction area may be micro lenses having a meansphere of 2.75 D.

The optical elements on the circle of diameter 20 mm and centered on theoptical center of the refraction area may be micro lenses having a meansphere of 4.75 D.

The optical elements on the circle of diameter 30 mm and centered on theoptical center of the refraction area may be micro lenses having a meansphere of 5.5 D.

The optical elements on the circle of diameter 40 mm and centered on theoptical center of the refraction area may be micro lenses having a meansphere of 5.75 D.

The mean cylinder of the different micro lenses may be adjusted based onthe shape of the retina of the person.

According to an embodiment of the invention, the refraction areacomprises a far vision reference point, a near vision reference, and ameridian joining the far and near vision reference points. For example,the refraction area may comprise a progressive additional lens designadapted to the prescription of the person or adapted to slow down theprogression of the abnormal refraction of the eye of the person wearingthe lens element.

Preferably, according to such embodiment, the optical elements areconfigured so that in standard wearing conditions along any horizontalsection of the lens the mean sphere and/or the mean cylinder of theoptical elements increases from the intersection of said horizontalsection with the meridian line towards the peripheral part of the lens.

The meridian line corresponds to the locus of the intersection of themain gaze direction with the surface of the lens.

The mean sphere and/or the mean cylinder increase function along thesections may be different depending on the position of said sectionalong the meridian line.

In particular, the mean sphere and/or the mean cylinder increasefunction along the sections are unsymmetrical. For example, the meansphere and/or the mean cylinder increase function are unsymmetricalalong vertical and/or horizontal section in standard wearing conditions.

According to an embodiment of the invention, at least one of the opticalelements has a non-spherical optical function.

Preferably at least 50%, for example at least 80%, for example all, ofthe optical elements 14 have a non-spherical optical function.

In the sense of the invention, a “non-spherical optical function” is tobe understood as not having a single focus point.

Advantageously, such optical function of the optical element reduces thedeformation of the retina of the eye of the wearer, allowing to slowdown the progression of the abnormal refraction of the eye of the personwearing the lens element.

The at least one element having a non-spherical optical function istransparent.

Advantageously, the non-contiguous optical elements are not visible onthe lens element and do not affect the aesthetic of the lens element.

According to an embodiment of the invention, the lens element maycomprise an ophthalmic lens bearing the refraction area and a clip-onbearing the plurality of at least three optical elements adapted to beremovably attached to the ophthalmic lens when the lens element is worn.Advantageously, when the person is in a far distance environment,outside for example, the person may separate the clip-on from theophthalmic lens and eventually substitute a second clip-on free of anyof at least three optical elements. For example, the second clip-on maycomprise a solar tint. The person may also use the ophthalmic lenswithout any additional clip-on.

The optical element may be added to the lens element independently oneach surface of the lens element.

One can add these optical elements on a defined array like square orhexagonal or random or other.

The optical element may cover specific zones of the lens element, likeat the center or any other area.

The optical element density or the quantity of power may be adjusteddepending on zones of the lens element. Typically, the optical elementmay be positioned in the periphery of the lens element, in order toincrease the effect of the optical element on myopia control, so as tocompensate peripheral defocus due to the peripheral shape of the retinafor example.

According to a preferred embodiment of the invention, every circularzone having a radius comprised between 2 and 4 mm comprising ageometrical center located at a distance of the optical center of thelens element greater or equal to said radius +5 mm, the ratio betweenthe sum of areas of the parts of optical elements located inside saidcircular zone and the area of said circular zone is comprised between20% and 70%, preferably between 30% and 60%, and more preferably between40% and 50%.

The optical elements can be made using different technologies likedirect surfacing, molding, casting or injection, embossing, filming, orphotolithography etc . . . .

According to an embodiment of the invention, at least one, for exampleall, of the optical elements has a shape configured so as to create acaustic in front of the retina of the eye of the person. In other words,such optical element is configured so that every section plane where thelight flux is concentrated if any, is located in front of the retina ofthe eye of the person.

According to an embodiment of the invention, the at least one, forexample all, of the optical element having a non-spherical opticalfunction is a multifocal refractive micro-lens.

In the sense of the invention, a “micro-lens” has a contour shape beinginscribable in a circle having a diameter greater than or equal to 0.8mm and smaller than or equal to 3.0 mm, preferably greater than or equalto 1.0mm and smaller than 2.0 mm.

In the sense of the invention, an optical element is “multifocalrefractive micro-lens” includes bifocals (with two focal powers),trifocals (with three focal powers), progressive addition lenses, withcontinuously varying focal power, for example aspherical progressivesurface lenses.

According to an embodiment of the invention, at least one of the opticalelement, preferably more than 50%, more preferably more than 80% of theoptical elements are aspherical microlenses. In the sense of theinvention, aspherical microlenses have a continuous power evolution overtheir surface.

An aspherical microlens may have an asphericity comprised between 0.1Dand 3D. The asphericity of an aspherical microlens corresponds to theratio of optical power measured in the center of the microlens and theoptical power measured in the periphery of the microlens.

The center of the microlens may be defined by a spherical area centeredon the geometrical center of the microlens and having a diametercomprised between 0.1 mm and 0.5 mm, preferably equal to 2.0 mm.

The periphery of the microlens may be defined by an annular zonecentered on the geometrical center of the microlens and having an innerdiameter comprised between 0.5 mm and 0.7 mm and an outer diametercomprised between 0.70 mm and 0.80 mm.

According to an embodiment of the invention, the aspherical microlenseshave an optical power in their geometrical center comprised between 2.0Dand 7.0D in absolute value, and an optical power in their peripherycomprised between 1.5D and 6.0D in absolute value.

The asphericity of the aspherical microlenses before the coating of thesurface of the lens element on which the optical elements are disposedmay vary according to the radial distance from the optical center ofsaid lens element.

Additionally, the asphericity of the aspherical microlenses after thecoating of the surface of the lens element on which the optical elementsare disposed may further vary according to the radial distance from theoptical center of said lens element.

According to an embodiment of the invention, the at least one multifocalrefractive micro-lens has a toric surface. A toric surface is a surfaceof revolution that can be created by rotating a circle or arc about anaxis of revolution (eventually positioned at infinity) that does notpass through its center of curvature.

Toric surface lenses have two different radial profiles at right anglesto each other, therefore producing two different focal powers.

Toric and spheric surface components of toric lenses produce anastigmatic light beam, as opposed to a single point focus.

According to an embodiment of the invention, the at least one of theoptical element having a non-spherical optical function, for exampleall, of the optical elements is a toric refractive micro-lens. Forexample, a toric refractive micro-lens with a sphere power value greaterthan or equal to 0 diopter (δ) and smaller than or equal to +5 diopters(δ), and cylinder power value greater than or equal to 0.25 Diopter (δ).

As a specific embodiment, the toric refractive microlens may be a purecylinder, meaning that minimum meridian power is zero, while maximummeridian power is strictly positive, for instance less than 5 Diopters.

According to an embodiment of the invention, at least one, for exampleall, of the optical element, is made of a birefringent material. Inother words, the optical element is made of a material having arefractive index that depends on the polarization and propagationdirection of light. The birefringence may be quantified as the maximumdifference between refractive indices exhibited by the material.

According to an embodiment of the invention, at least one, for exampleall of the optical element, has discontinuities, such as a discontinuoussurface, for example Fresnel surfaces and/or having a refractive indexprofile with discontinuities.

FIG. 3 represents an example of a Fresnel height profile of an opticalelement that may be used for the invention.

According to an embodiment of the invention, at least one, for exampleall of the optical element, is made of a diffractive lens.

FIG. 4 represents an example of a diffractive lens radial profile of anoptical element that may be used for the invention.

At least one, for example all, of the diffractive lenses may comprise ametasurface structure as disclosed in WO2017/176921.

The diffractive lens may be a Fresnel lens whose phase function Ψ(r) hasπ phase jumps at the nominal wavelength, as seen in FIG. 5. One may givethese structures the name “π-Fresnel lenses” for clarity's sake, asopposition to unifocal Fresnel lenses whose phase jumps are multiplevalues of 2π. The π-Fresnel lens whose phase function is displayed inFIG. 5 diffracts light mainly in two diffraction orders associated todioptric powers 0 δ and a positive one P, for example 3 δ.

According to an embodiment of the invention, at least one, for exampleall of the optical element, is a multifocal binary component.

For example, a binary structure, as represented in FIG. 6a , displaysmainly two dioptric powers, denoted −P/2 and P/2. When associated to arefractive structure as shown in FIG. 6b , whose dioptric power is P/2,the final structure represented in FIG. 6c has dioptric powers 0 δ andP. The illustrated case is associated to P=3 δ.

According to an embodiment of the invention, at least one, for exampleall of the optical element, is a pixelated lens. An example ofmultifocal pixelated lens is disclosed in Eyal Ben-Eliezer et al,APPLIED OPTICS, Vol. 44, No. 14, 10 May 2005.

According to an embodiment of the invention, at least one, for exampleall of the optical element, has an optical function with high orderoptical aberrations. For example, the optical element is a micro-lenscomposed of continuous surfaces defined by Zernike polynomials.

The invention has been described above with the aid of embodimentswithout limitation of the general inventive concept.

Many further modifications and variations will be apparent to thoseskilled in the art upon making reference to the foregoing illustrativeembodiments, which are given by way of example only and which are notintended to limit the scope of the invention, that being determinedsolely by the appended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. The mere fact that different features are recited in mutuallydifferent dependent claims does not indicate that a combination of thesefeatures cannot be advantageously used. Any reference signs in theclaims should not be construed as limiting the scope of the invention.

The invention claimed is:
 1. A lens element for wearing in front of aneye of a person comprising: a refraction area having a first refractivepower corresponding to a prescription for correcting an abnormalrefraction of said eye of the person and a second refractive powerdifferent from the first refractive power; and at least three opticalelements, at least one optical element of the at least three opticalelements having an optical function of not focusing an image on a retinaof the eye to slow down progression of abnormal refraction of the eye,wherein the at least three optical elements are configured so that alongat least one section of the lens element, a mean sphere of the at leastthree optical elements increases from a first point of the at least onesection towards a peripheral part of the at least one section by atleast 0.5D, and decreases from a second point of the at least onesection towards the peripheral pan of the at least one section by atleast 0.5D, the second point being closer to the peripheral part of theat least one section than the first point.
 2. The lens element accordingto claim 1, wherein a difference between the first refractive power andthe second refractive power is greater than or equal to 0.5D.
 3. Thelens element according to claim 1, wherein the refractive area is formedas an area other than areas formed as a plurality of optical elements.4. The lens element according to claim 1, wherein at least one opticalelement of the at least three optical elements has a non-sphericaloptical function.
 5. The lens element according to claim 1, wherein atleast one optical element of the at least three optical elements has anoptical function of focusing an image on a position other than a retina.6. The lens element according to claim 1, wherein, in the refractivearea, a refractive power has a continuous variation.
 7. The lens elementaccording to claim 1, wherein, in the refractive area, a refractivepower has at least one discontinuity.
 8. The lens element according toclam 1, wherein the lens element is divided into five complementaryzones, a central zone having a power being equal to the first refractivepower and four quadrants at 45°, at least one of the four quadrantshaving a refractive power equal to the second refractive power.
 9. Thelens element according to claim 8, wherein the central zone includes aframing reference point that faces a pupil of the person gazing straightahead in standard wearing conditions and has a diameter greater than 4mm and smaller than 20 mm.
 10. The lens element according to claim 8,wherein at least a lower part of the four quadrants has the secondrefractive power.
 11. The lens element according to claim 1, wherein therefraction area has a progressive addition dioptric function.
 12. Thelens element according to claim 8, wherein at least one of a temporaland nasal quadrant of the four quadrants has the second refractivepower.
 13. The lens element according to claim 8, wherein the fourquadrants have a concentric power progression.
 14. The lens elementaccording to claim 1, wherein for every circular zone having a radiuscomprised between 2 mm and 4 mm including a geometrical center locatedat a distance of a framing reference that faces a pupil of the persongazing straight ahead in standard wearing conditions greater or equal tosaid radius +5 mm, a ratio between a sum of areas of parts of opticalelements located inside said circular zone and an area of said circularzone is comprised between 20% and 70% of the lens element.
 15. The lenselement according to claim 1, wherein the at least three opticalelements are non-contiguous.